Display device

ABSTRACT

According to one embodiment, a display device includes a display panel, a light emitting element, a light guide layer and a first optical layer. The display panel includes a first substrate, a second substrate opposed to the first substrate, and a polymer dispersed liquid crystal layer which is held between the first substrate and the second substrate and contains a polymer and a liquid crystal molecule. The light guide layer has a first surface opposed to the display panel, and an edge opposed to the light emitting element. The first optical layer is located between the display panel and the light guide layer. A refractive index of the first optical layer is lower than a refractive index of the light guide layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2017-152648, filed Aug. 7, 2017, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a display device.

BACKGROUND

Recently, various display devices using polymer dispersed liquidcrystals (hereinafter referred to also as PDLCs) which can switchbetween a scattering state in which entering light is scattered and atransmitting state in which entering light is transmitted have beenproposed. In a display device using PDLCs, an illumination device whichemits light to a display panel may be arranged on the side of an edge ofthe display panel in some cases. In this structure, due to scattering oflight in the display panel, etc., the luminance of an area which is farfrom a light emitting element may become lower than the luminance of anarea which is close to the light emitting element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an example of the structure of a displaydevice DSP according to the present embodiment.

FIG. 2 is a sectional view of the display device DSP shown in FIG. 1.

FIG. 3 is a sectional view showing an example of the structure of adisplay panel PNL shown in FIG. 2.

FIG. 4 is a diagram schematically showing a transparent state of aliquid crystal layer 30.

FIG. 5 is a diagram schematically showing a scattering state of theliquid crystal layer 30.

FIG. 6 is a sectional view of the display device DSP when the liquidcrystal layer 30 is in the transparent state.

FIG. 7 is a sectional view of the display device DSP when the liquidcrystal layer 30 is in the scattering state.

FIG. 8 is a plan view showing an example of a pixel PX.

FIG. 9 is a sectional view of the pixel PX taken along line A-B shown inFIG. 8.

FIG. 10 is a plan view showing an example of the relationship between anopening OP of an optical layer 60 and a pixel electrode 13.

FIG. 11 is a sectional view showing a method of forming a light guideelement LG.

FIG. 12 is a plan view showing another example of the optical layer 60.

FIG. 13 is a plan view showing another example of the optical layer 60.

FIG. 14 is a plan view showing another example of the optical layer 60.

FIG. 15 is a sectional view showing another example of the displaydevice DSP.

FIG. 16 is a sectional view showing another example of the displaydevice DSP.

FIG. 17 is a sectional view showing another example of the displaydevice DSP.

FIG. 18 is a diagram showing the main structural elements of the displaydevice DSP shown in FIG. 1.

DETAILED DESCRIPTION

In general, according to one embodiment, there is provided a displaydevice including a display panel, a light emitting element, a lightguide layer and a first optical layer. The display panel includes afirst substrate, a second substrate which is opposed to the firstsubstrate, and a polymer dispersed liquid crystal layer which is heldbetween the first substrate and the second substrate and contains apolymer and a liquid crystal molecule. The light guide layer has a firstsurface which is opposed to the display panel, and an edge which isopposed to the light emitting element. The first optical layer islocated between the display panel and the light guide layer. Arefractive index of the first optical layer is lower than a refractiveindex of the light guide layer.

According to another embodiment, there is provided a display deviceincluding a display panel, a light emitting element, a light guide layerand a first optical layer. The display panel includes a first substrate,a second substrate which is opposed to the first substrate, a sealantwhich is located between the first substrate and the second substrate,and a polymer dispersed liquid crystal layer which is located within anarea surrounded by the sealant and contains a polymer and a liquidcrystal molecule. The light guide layer has a first surface which isopposed to the display panel, and a first edge which is opposed to thelight emitting element. The first optical layer is arranged along thefirst surface between the display panel and the light guide layer andextends from the first edge to a position overlapping at least thesealant. A refractive index of the first optical layer is lower than arefractive index of the light guide layer.

According to still another embodiment, there is provided a displaydevice including a light emitting element, a light guide layer, adisplay panel, a second optical layer and a third optical layer. Thelight guide layer has a first surface, an edge which is opposed to thelight emitting element, and a second surface which is opposite to thefirst surface. The display panel has a third surface which is oppositeto a surface opposed to the first surface, and includes a polymerdispersed liquid crystal layer which contains a polymer and a liquidcrystal molecule. The second optical layer is opposed to the entiresecond surface. The third optical layer is opposed to the entire thirdsurface. A refractive index of the second optical layer and a refractiveindex of the third optical layer are lower than a refractive index ofthe light guide layer.

Embodiments will be described hereinafter with reference to theaccompanying drawings. Incidentally, the disclosure is merely anexample, and proper changes within the spirit of the invention, whichare easily conceivable by a skilled person, are included in the scope ofthe invention as a matter of course. In addition, in some cases, inorder to make the description clearer, the widths, thicknesses, shapes,etc., of the respective parts are schematically illustrated in thedrawings, compared to the actual modes. However, the schematicillustration is merely an example, and adds no restrictions to theinterpretation of the invention. Besides, in the specification anddrawings, the structural elements having functions, which are identicalor similar to the functions of the structural elements described inconnection with preceding drawings, are denoted by like referencenumerals, and an overlapping detailed description is omitted unlessotherwise necessary.

FIG. 1 is a plan view showing an example of the structure of a displaydevice DSP according to the present embodiment. In the drawings, a firstdirection X and a second direction Y intersect each other, and a thirddirection Z intersects the first direction X and the second direction Y.The first direction X, the second direction Y and the third direction Zorthogonally intersect each other, for example, but may intersect eachother at an angle other than 90 degrees. In the present specification,the direction of the pointing end of an arrow indicating the thirddirection Z is referred to as above, and the opposition direction to thepointing end of the arrow is referred to as below. Such expressions as“a second member above a first member” and “a second member below afirst member” mean that the second member may be in contact with thefirst member or may be apart from the first member. Further, assumingthat a viewing position to view the display device DSP is located on thepointing end side of the arrow indicating the third direction Z, a viewin an X-Y plane defined by the first direction X and the seconddirection Y from this viewing position is defined as a planar view.

In the present embodiment, a display device adopting polymer dispersedliquid crystals will be described as an example of the display device.The display device DSP includes a display panel PNL, wiring substratesF1 to F3, a light guide element LG and a light source unit which is notshown in this drawing.

The display panel PNL includes a first substrate SUB1 and a secondsubstrate SUB2. The first substrate SUB1 and the second substrate SUB2overlap each other in a planar view. The display panel PNL includes adisplay area DA which displays an image, and a frame-like non-displayarea NDA which surrounds the display area DA. The display area DA islocated in an area in which the first substrate SUB1 and the secondsubstrate SUB2 overlap each other. The display panel PNL includes nscanning lines G (G1 to Gn) and m signal lines S (S1 to Sm) in thedisplay area DA. Both n and m are positive integers, and n and m may beequal to each other or may be different from each other. The scanninglines G extend in the first direction X and are arranged at intervals inthe second direction Y. The signal lines S extend in the seconddirection Y and are arranged at intervals in the first direction X.

The first substrate SUB1 has edges E11 and E12 which extend in the firstdirection X and edges E13 and E14 which extend in the second directionY. The second substrate SUB2 has edges E21 and E22 which extend in thefirst direction X and edges E23 and E24 which extend in the seconddirection Y. In a planar view, the edge E11 and the edge E21, the edgeE13 and the edge E23, and the edge E14 and the edge E24 overlap eachother, respectively, in the example illustrated but may not overlap eachother. The edge E22 is located between the edge 512 and the display areaDA in a planar view. The first substrate SUB1 has an extension portionEx between the edge E12 and the edge E22.

The wiring substrates F1 to F3 are connected to the extension portion Exand are arranged in this order in the first direction X. The wiringsubstrate F1 includes a gate driver GD1. The wiring substrate F2includes a source driver SD. The wiring substrate F3 includes a gatedriver GD2. The wiring substrate F1 to F3 may be replaced with a singlewiring substrate.

The signal lines S are drawn to the non-display area NDA and areconnected to the source driver SD. The scanning lines G are drawn to thenon-display area NDA and are connected to the gate drivers GD1 and GD2.In the example illustrated, the odd-numbered scanning lines G are drawnbetween the edge E14 and the display area DA and are connected to thegate driver GD2. Further, the even-numbered scanning lines G are drawnbetween the edge E13 and the display area DA and are connected to thegate driver GD1. The connection relationship of the gate drivers GD1 andGD2 to the scanning lines G are not limited to that of the exampleillustrated.

The light guide element LG is located below the display panel PNL. Forexample, the light guide element LG has the same shape as that of thefirst substrate SUB1 and overlaps the entire first substrate SUB1. Thelight guide element LG has edges E31 and E32 which extend in the firstdirection X and edges E33 and E34 which extend in the second directionY. In the example illustrated, the edge E31 overlaps the edges E11 andE21, the edge E32 overlaps the edge E12, the edge E33 overlaps the edgesE13 and E23, and the edge E34 overlaps the edges E14 and E24.

FIG. 2 is a sectional view of the display device DSP shown in FIG. 1.Here, only the major part will be explained in a cross-section of thedisplay device DSP in a Y-Z plane defined by the second direction Y andthe third direction Z.

The display device DSP includes a light source unit LU in addition tothe display panel PNL, the wiring substrates F1 to F3 and the lightguide element LG.

The display panel PNL includes a liquid crystal layer 30 held betweenthe first substrate SUB1 and the second substrate SUB2. The firstsubstrate SUB1 and the second substrate SUB2 are attached together by asealant 40. The liquid crystal layer 30 is located within an areasurrounded by the sealant 40. In the example illustrated, the extensionportion Ex extends beyond the second substrate SUB2 in the seconddirection Y.

The light source unit LU is located on the extension portion Ex side inthe second direction Y, for example. The light source unit LU includes alight emitting element LS as a light source, a wiring substrate F4, etc.The light emitting element LS is connected to the wiring substrate F4.In the example illustrated, the wiring substrate F4 and the lightemitting element LS are located below the wiring substrates F1 to F3.

The light guide element LG is opposed to the first substrate SUB1, forexample. The light guide element LG includes a light guide layer 50 andan optical layer 60. The light guide layer 50 has a first surface 50Awhich is opposed to the display panel PNL and a second surface 50B whichis opposite to the first surface 50A. The edge E32 is opposed to thelight emitting element LS. For example, the light emitting element LS isonly opposed to the light guide layer 50. In the example illustrated,the first surface 50A and the second surface 50B are surfaces parallelto the X-Y plane. The light guide layer 50 is formed of a transparentmaterial such as glass, acrylic or polycarbonate. Non-transparentmembers are not provided below the second surface 50B.

The optical layer 60 is located between the display panel PNL and thelight guide layer 50. In the example illustrated, the optical layer 60contacts the first surface 50A. The optical layer 60 overlaps at leastthe extension portion Ex. In the example illustrated, the optical layer60 also overlaps the sealant 40. That is, the optical layer 60 extendsfrom the edge E32 to a position overlapping the sealant 40 in the seconddirection Y. The optical layer 60 also overlaps the sealant 40 on theedge E31 side. The optical layer 60 is formed of fluorine resin orsilicon resin, and is transparent and is a haze-free material.

In the present embodiment, the optical layer 60 has a plurality ofopenings OP (OP1, OP2 and OP3). The openings OP are formed in areaswhich overlap the liquid crystal layer 30. The opening OP2 is fartherfrom the light emitting element LS than the opening OP1. The opening OP3is farther from the light emitting element LS than the opening OP2. Inthe example illustrated, a width W2 of the opening OP2 is greater than awidth W1 of the opening OP1. A width W3 of the opening OP3 is greaterthan the width W2. The widths here correspond to a dimension in thesecond direction Y.

The light guide element LG is attached to the display panel PNL by atransparent adhesive layer 70. In the example illustrated, the adhesivelayer 70 is interposed between the display panel PNL and the opticallayer 60 and is also provided in the openings OP. That is, the adhesivelayer 70 contacts the display panel PNL, the optical layer 60 and thelight guide layer 50. Although not shown in the drawing, the opticallayer 60 may contact the display panel PNL. Further, the adhesive layer70 may be interposed between the optical layer 60 and the light guidelayer 50. Still further, the openings OP may be filled and flattenedwith an overcoat material having the same refractive index as that ofthe light guide element LG, in place of the adhesive layer 70. In thiscase, the light guide element LG may be attached to the display panelPNL by a film-like adhesive sheet having the same refractive index asthose of the first substrate SUB1 and the overcoat.

In the present embodiment, the refractive index of the optical layer 60is lower than the refractive index of the light guide layer 50. Further,the refractive index of air is lower than the refractive index of thelight guide layer 50. In the present structure, light which enters thelight guide layer 50 from the light emitting element LS is reflected atthe border of the light guide layer 50 and the optical layer 60 (thatis, by the first surface 50A) and at the border of the light guide layer50 and air (that is, by the second surface 50B) and travels through thelight guide layer 50. As described above, the light emitting element LSis only opposed to the light guide layer 50, and therefore the lightemitted from the light emitting element LS hardly enters the opticallayer 60, the adhesive layer 70 and the first substrate SUB1 directly.On the other hand, the refractive index of the adhesive layer 70 ishigher than the refractive index of the optical layer 60 and issubstantially equal to the refractive index of the light guide layer 50.Therefore, the light traveling through the light guide layer 50 ishardly reflected at the border of the light guide layer 50 and theadhesive layer 70. In other words, part of the light traveling throughthe light guide layer 50 enters the display panel PNL through theopenings OP.

In the example illustrated, of the light entering the light guide layer50, light LA which travels toward the first surface 50A side isreflected at the border of the light guide layer 50 and the opticallayer 60. After reflected at the border of the light guide layer 50 andair and at the border of the light guide layer 50 and the optical layer60 repeatedly, the light enters the display panel PNL through theopening OP3. Of the light entering the light guide layer 50, light LBwhich travels toward the second surface 50B side is reflected at theborder of the light guide layer 50 and air and then enters the displaypanel PNL thorough the opening OP1. Although not shown in the drawing,part of the light traveling through the light guide layer 50 may enterthe display panel PNL through the opening OP2 in some cases. Further,part of the light traveling through the display panel PNL may enter thelight guide layer 50 through the openings OP in some cases.

FIG. 3 is a sectional view showing an example of the structure of thedisplay panel PNL shown in FIG. 2. The first substrate SUB1 includes atransparent substrate 10, a wiring line 11, an insulating layer 12, apixel electrode 13 and an alignment film 14. The second substrate SUB2includes a transparent substrate 20, a common electrode 21 and analignment film 22. Note that the second substrate SUB2 does not includea light-shielding layer which overlaps the wiring line 11.

The transparent substrates 10 and 20 are Insulating substrates such asglass substrates or plastic substrates. The wiring line 11 is formed ofa non-transparent metal such as molybdenum, tungsten, aluminum, titaniumor silver. The wiring line 11 extend in the first direction X in theexample illustrate but may extend in the second direction Y. Theinsulating layer 12 is formed of a transparent insulating material. Thepixel electrode 13 and the common electrode 21 are formed of atransparent conductive material such as indium tin oxide (ITO) or indiumzinc oxide (IZO). Each pixel electrode 13 is arranged in each pixel PX.The common electrode 21 is arranged over the pixels PX. The alignmentfilms 14 and 22 may be horizontal alignment films having the force ofregulating alignment substantially parallel to the X-Y plane or may bevertical alignment films having the force of regulating alignmentsubstantially parallel to the third direction Z.

The liquid crystal layer 30 is located between the alignment film 14 andthe alignment film 22. The liquid crystal layer 30 includes polymerdispersed liquid crystals containing polymers 31 as polymer compoundsand liquid crystal molecules 32. For example, the polymer 31 is a liquidcrystal polymer. A polymer is obtained, for example, by polymerizing aliquid crystal monomer in the state of being aligned in a predetermineddirection by the alignment regulation forces of the alignment films 14and 22. For example, the alignment treatment directions of the alignmentfilms 14 and 22 correspond to the first direction X, the alignment films14 and 22 have alignment regulation forces in the first direction X.Therefore, the polymers 31 are formed into streaks which extend in thefirst direction X. The liquid crystal molecules 32 are dispersed in thegap between the polymers 31 and are aligned such that major axes thereofare aligned with the first direction X. In the enlarged part of thedrawing, the polymer 31 is shown by rising diagonal lines and the liquidcrystal molecule 32 is shown by falling diagonal lines.

Each of the polymer 31 and the liquid crystal molecule 32 has an opticalanisotropy or a refractive index anisotropy. The liquid crystal molecule32 may be a positive type liquid crystal molecule having a positivedielectric constant anisotropy or may be a negative type liquid crystalmolecule having a negative dielectric constant anisotropy. The polymer31 and the liquid crystal molecule 32 respond to an electric fielddifferently. The polymer 31 is less responsive to an electric field thanthe liquid crystal molecule 32 to an electric field.

FIG. 4 is a diagram schematically showing a transparent state of theliquid crystal layer 30. The example illustrated corresponds to a statewhere voltage is not applied to the liquid crystal layer 30 (a statewhere the electric potential difference between the pixel electrode 13and the common electrode 21 is substantially zero, for example). Anoptical axis Ax1 of the polymer 31 and an optical axis Ax2 of the liquidcrystal molecule 32 are parallel to each other. In the exampleillustrated, the optical axis Ax1 and the optical axis Ax2 are parallelto the first direction X. The polymer 31 and the liquid crystal molecule32 have substantially the same refractive index anisotropy. That is, theordinary refractive index of the polymer 31 and the ordinary refractiveindex of the liquid crystal molecule 32 are substantially equal to eachother, and the extraordinary refractive index of the polymer 31 and theextraordinary refractive index of the liquid crystal molecule 32 aresubstantially equal to each other. Therefore, the polymer 31 and theliquid crystal molecule 32 have hardly any refractive index differencein all directions including the first direction X, the second directionY and the third direction Z. Consequently, light L1 which have enteredthe liquid crystal layer 30 in the third direction Z is hardly scatteredin the liquid crystal layer 30 and is transmitted through the liquidcrystal layer 30. Similarly, light L2 and light L3 which have enteredthe liquid crystal layer 30 in oblique directions which are inclinedwith respect to the third direction Z are hardly scattered in the liquidcrystal layer 30. Therefore, high transparency can be achieved. Thestate shown in FIG. 4 is referred to as a transparent state. Forexample, light L3 corresponds to the light emitted from the lightemitting element LS shown in FIG. 2, and is hardly scattered in theliquid crystal layer 30 and travels in the opposite direction to thedirection of the arrow of the second direction Y.

FIG. 5 is a diagram schematically showing a scattering state of theliquid crystal layer 30. The example illustrated corresponds to a statewhere voltage is applied to the liquid crystal layer 30 (a state wherethe electric potential difference between the pixel electrode 13 and thecommon electrode 21 is greater than or equal to a threshold value, forexample). As described above, the polymer 31 is less responsive to anelectric field than the liquid crystal molecule 32 to an electric field.For example, the alignment direction of the polymer 31 hardly changesregardless of the presence or absence of an electric field. On the otherhand, the alignment direction of the liquid crystal molecule 32 changesin accordance with an electric field in a state where voltage higherthan or equal to the threshold value is applied to the liquid crystallayer 30. That is, the optical axis Ax1 is substantially parallel to thefirst direction X, whereas the optical axis Ax2 is inclined with respectto the first direction X as shown in the drawing. If the liquid crystalmolecule 32 is a positive type liquid crystal molecule, the liquidcrystal molecule 32 is aligned such that a major axis thereof is alignedwith an electric field. An electric field between the pixel electrode 13and the common electrode 21 is produced in the third direction Z.Therefore, the liquid crystal molecule 32 is aligned such that a majoraxis thereof or the optical axis Ax2 is aligned with the third directionZ. That is, the optical axes Ax1 and Ax2 intersect each other.Therefore, a large refractive index difference is caused between thepolymer 31 and the liquid crystal molecule 32 in all directionsincluding the first direction X, the second direction Y and the thirddirection Z. Accordingly, the light L1 to the light L3 which haveentered the liquid crystal layer 30 are scattered in the liquid crystallayer 30. The state shown in FIG. 5 is referred to as a scatteringstate.

FIG. 6 is a sectional view of the display device DSP when the liquidcrystal layer 30 is in the transparent state. The light emitted from thelight emitting element LS enters the light guide layer 50 from the edgeE32 and travels through the light guide layer 50. Of the light travelingthrough the light guide layer 50, light L11 which enters the displaypanel PNL from an opening OP11 and light L12 which enters the displaypanel PNL from an opening OP12 travel through the liquid crystal layer30, the transparent substrate 10, the transparent substrate 20, etc. Theopening OP11 is closer to the light emitting element LS than the openingOP12 in the second direction Y.

In the example illustrated, after the light L11 enters the liquidcrystal layer 30 which overlaps a pixel electrode 131, the light L11 isreflected at the border of the transparent substrate 20 and air (thatis, by an upper surface 20T of the transparent substrate 20) and entersthe liquid crystal layer 30 which overlaps a pixel electrode 132.Subsequently, the light L11 is reflected at the border of the adhesivelayer 70 and the optical layer 60 (that is, by an upper surface 60A ofthe optical layer 60) and enters the liquid crystal layer 30 whichoverlaps a pixel electrode 133. Further, in the example illustrated, thelight L12 enters the liquid crystal layer 30 which overlaps the pixelelectrode 133.

The liquid crystal layer 30 which overlaps the wiring line 11 and theliquid crystal layer 30 which overlaps the pixel electrodes 131, 132 and133 are in the transparent state. Therefore, the light L11 and the lightL12 are hardly scattered in the liquid crystal layer 30. Consequently,the light L11 and the light L12 hardly leak from the second surface 50Bof the light guide layer 50 and the upper surface 20T of the transparentsubstrate 20 and travel through the display panel PNL.

External light LE which enters the display panel PNL is hardly scatteredin the liquid crystal layer 30 and is transmitted through the liquidcrystal layer 30. That is, external light LE which has entered thedisplay panel PNL from the second surface 50B is transmitted through theupper surface 20T, and external light LE which has entered the displaypanel PNL from the upper surface 20T is transmitted through the secondsurface 50B. Therefore, when the user views the display panel PNL fromthe upper surface 20T side, the user can see a view on the secondsurface 50B side through the display panel PNL. Similarly, when the userviews the display panel PNL from the second surface 50B side, the usercan see a view on the upper surface 20T side through the display panelPNL.

FIG. 7 is a sectional view of the display device DSP when the liquidcrystal layer 30 is in the scattering state. The light emitted from thelight emitting element LS enters the light guide layer 50 from the edgeE32 and travels through the light guide layer 50. Of the light travelingthrough the light guide layer 50, light L21 which enters the displaypanel PNL from the opening OP11 and light L22 which enters the displaypanel PNL from the opening OP12 travel through the liquid crystal layer30, the transparent substrate 10, the transparent substrate 20, etc.

In the example illustrated, the liquid crystal layer 30 which overlapsthe wiring line 11 is maintained in the transparent state. Further, theliquid crystal layer 30 which overlaps the pixel electrode 131 is in thetransparent state. Therefore, the light L21 is hardly scattered in areasof the liquid crystal layer 30 which overlap the wiring line 11 and thepixel electrode 131. On the other hand, the liquid crystal layer 30which overlaps the pixel electrode 132 is in the scattering state.Therefore, the light L21 is scattered in an area of the liquid crystallayer 30 which overlaps the pixel electrode 132. One part of the lightL21 referred to as scattering light L211 is transmitted through theupper surface 20T, another part of the light L21 referred to asscattering light L212 is transmitted through the second surface 50B, andthe other scattering light travels through the display panel PNL.

Meanwhile, in the example illustrated, the light L22 enters an area ofthe liquid crystal layer 30 which overlaps the pixel electrode 133. Theliquid crystal layer 30 which overlaps the pixel electrode 133 is in thetransparent state. Therefore, the light L22 is hardly scattered in areasof the liquid crystal layer 30 which overlap the wiring line 11 and thepixel electrode 133. Therefore, the light L22 hardly leaks from thesecond surface 50B and the upper surface 20T and travels through thedisplay panel PNL. As described above, even if part of the light L21 isscattered in the liquid crystal layer 30, the light L22 enters an areaof the liquid crystal layer 30 which is far from the light emittingelement LS than an area of the liquid crystal layer 30 in the scatteringstate.

In the area overlapping the pixel electrode 131, external light LE1which enters the display panel PNL is hardly scattered in the liquidcrystal layer 30 and is transmitted through the liquid crystal layer 30similarly to the external light LE shown in FIG. 6. In the areaoverlapping the pixel electrode 132, external light LE2 which entersfrom the second surface 50B is scattered in the liquid crystal layer 30,and part of the external light LE2 referred to as light LE21 istransmitted through the upper surface 20T. Further, external light LE3which enters from the upper surface 20T is scattered in the liquidcrystal layer 30, and part of the external light LE3 referred to aslight LE31 is transmitted through the second surface 50B. Therefore,when the user views the display panel PNL from the upper surface 20Tside, the user can visually recognize the color of the light L21 in thearea overlapping the pixel electrode 132. Further, since the externallight LE21 is transmitted through the display panel PNL, the user cansee a view on the second surface 50B side through the display panel PNL.Similarly, when the user views the display panel PNL from the secondsurface 50B side, the user can visually recognize the color of the lightL21 in the area overlapping the pixel electrode 132. Further, since theexternal light LE31 is transmitted through the display panel PNL, theuser can see a view on the upper surface 20T side through the displaypanel PNL.

In the area overlapping the pixel electrode 131, since the liquidcrystal layer 30 is in the transparent state, the color of the light L21is hardly visually recognized, and the user can see a view behind thedisplay panel PNL through the display panel PNL. Further, in the areaoverlapping the pixel electrode 133, since the liquid crystal layer 30is in the transparent state, the color of the light L22 is hardlyvisually recognized, and the user can see a view behind the displaypanel PNL through the display panel PNL.

FIG. 8 is a plan view showing an example of the pixel PX. In the exampleillustrated, the pixel PX is partitioned with two signal lines Sarranged in the first direction X and two scanning lines G arranged inthe second direction Y.

The pixel PX includes a switching element SW and the pixel electrode 13.The switching element SW is a thin-film transistor, for example, and iselectrically connected to the scanning line G and the signal line S.More specifically, the switching element SW includes a gate electrodeGE, a source electrode SE and a drain electrode DE. The gate electrodeGE is formed integrally with the scanning line G. The switching elementSW is a bottom-gate type in which the gate electrode GE is located belowa semiconductor layer SC in the example illustrated but may be atop-gate type in which the gate electrode GE is located above thesemiconductor layer SC. The semiconductor layer SC is formed ofamorphous silicon, for example, but may be formed of polycrystallinesilicon, an oxide semiconductor, etc. The source electrode SE is formedintegrally with the signal line S and contacts the semiconductor layerSC. The drain electrode DE is separated from the source electrode SE andcontacts the semiconductor layer SC. The pixel electrode 13 overlaps thedrain electrode DE from above and contacts the drain electrode DE in acontact hole CH.

Further, a capacitance line C is arranged between two scanning lines G.The pixel electrode 13 overlaps the capacitance line C from above. Aportion in which the capacitance line C and the pixel electrode 13overlap each other produces storage capacitance.

FIG. 9 is a sectional view of the pixel PX taken along line A-B shown inFIG. 8.

In the first substrate SUB1, the gate electrode GE and the scanning lineG which is not shown in the drawing are located on the transparentsubstrate 10 and correspond to the wiring line 11 shown in FIG. 3, forexample. An insulating layer 121 covers the gate electrode GE and thetransparent substrate 10. The semiconductor layer SC is located on theinsulating layer 121 directly above the gate electrode GE. The sourceelectrode SE and the drain electrode DE are located on the insulatinglayer 121 and contacts the semiconductor layer SC. An insulating layer122 covers the semiconductor layer SC, the source electrode SE, thedrain electrode DE and the insulating layer 121. An insulating layer 123covers the insulating layer 122. The insulating layers 121 to 123correspond to the insulating layer 12 shown in FIG. 3, for example. Theinsulating layers 121 and 122 are formed of a transparent inorganicinsulating material such as silicon nitride or silicon oxide. Theinsulating layer 123 is formed of a transparent organic insulatingmaterial such as acrylic resin. The pixel electrode 13 is located on theinsulating layer 123. The pixel electrode 13 contacts the drainelectrode DE in the contact hole CH which penetrates the insulatinglayers 122 and 123. An alignment film 14 covers the pixel electrode 13and the insulating layer 123.

In the second substrate SUB2, the common electrode 21 is located belowthe transparent substrate 20. An alignment film 22 covers the commonelectrode 21. The liquid crystal layer 30 contacts the alignment films14 and 22.

FIG. 10 is a plan view showing an example of the relationship betweenthe opening OP of the optical layer 60 and the pixel electrode 13. Inthe example illustrated, a pixel electrode 13 a and a pixel electrode 13b are arranged in the second direction Y. The pixel electrode 13 a iscloser to the light emitting element LS than the pixel electrode 13 b.

Each of the pixel electrodes 13 a and 13 b overlaps the openings OP. Inthe example illustrated, openings OPa which overlap the pixel electrode13 a have the same shape and have substantially the same area. Further,openings OPb which overlap the pixel electrode 13 b have the same shapeand have substantially the same area.

In the present embodiment, a total of the areas (hereinafter referred toas the total area) of the openings OPb is larger than the total area ofthe openings OPa. In the example shown in FIG. 10, the number of theopenings OPb and the number of the openings OPa are equal to each other,but the area of each opening OPb is larger than the area of each openingOPa. Therefore, the total area of the openings OPb is larger than thetotal area of the openings OPa. If the total area of the openings OPoverlapping the pixel electrode 13 per unit area of pixel electrode 13is defined as an aperture ratio, the aperture ratio of the openings OPbis higher than the aperture ratio of the openings OPa.

In the example illustrated, the openings OP are not periodicallyarranged. In other words, the distances between one opening OP andopenings OP which are adjacent to the one opening OP are not the same.Some openings OP partially overlap the signal lines S, the scanninglines G and the pixel electrodes 13 a and 13 b. The openings OP have acircular shape in the example illustrated but may have any shape such asan elliptical shape, a polygonal shape or a shape consisting of acombination of a curve and a line. Further, the number of the openingsOPa and the number of the openings OPb are not limited to those of theexample illustrated.

According to the present embodiment, the display device DSP includes thelight guide element LG which includes the light guide layer 50 and theoptical layer 60 having the openings OP. The refractive index of theoptical layer 60 is lower than the refractive index of the light guidelayer 50. Therefore, part of the light traveling through the light guidelayer 50 is reflected at the border of the light guide layer 50 and theoptical layer 60 and is substantively confined within the light guidelayer 50, and therefore the light can be transmitted to an area which isfar from the light emitting element LS. Further, as the opening OP islocated farther from the light emitting element LS, the area of theopening OP becomes larger. According to this structure, the amount oflight which enters the display panel PNL from the light guide element LGnear the light emitting element LS can be reduced, and the amount oflight which enters the display panel PNL from the light guide element LGin the area far from the light emitting element LS can be increased.Therefore, even if the intensity of light which travels on the sidewhich is far from the light emitting element LS is lower than theintensity of light which travels on the side which is close to the lightemitting element LS, the difference of luminance caused by the distancefrom the light emitting element LS can be reduced, and degradation ofdisplay quality can be prevented.

Further, the optical layer 60 is provided entirely across an areaoverlapping the extension portion EX, that is, an area between the edgeE12 and the edge E22 in the second direction Y. Therefore, the lightemitted from the light emitting element LS can be prevented from leakingthrough the extension portion Ex, and the light can be used moreefficiently.

FIG. 11 is a sectional view showing a method of forming the light guideelement LG. As shown in FIG. 11(a), a transparent layer 600 formed of atransparent material is formed on the first surface 50A of the lightguide layer 50. The refractive index of the transparent layer 600 islower than the refractive index of the light guide layer 50.Subsequently, a resist layer R1 is formed on the transparent layer 600.A photomask PM is disposed on the resist layer R1 as shown in FIG.11(b). The photomask PM has a shielding portion PMA which blocksultraviolet light and has a transmitting portion PMP which transmitsultraviolet light. Subsequently, ultraviolet light is applied to thelight guide layer 50 through the photomask PM. An area of the resistlayer R1 which overlaps the shielding layer PMA is removed bylithography treatment as shown in FIG. 11(c). Subsequently, etchingprocessing is performed by using the resist layer R1 as a mask, and theoptical layer 60 having the openings OP is formed, and the light guideelement LG is formed. An adhesive layer 70 is formed entirely on thefirst surface 50A side as shown in FIG. 11(d). The adhesive layer 70contacts the optical layer 60 and also contacts the first surface 50A inthe openings OP. Subsequently, the light guide element LG is attached tothe display panel PNL via the adhesive layer 70.

Note that the method of forming the light guide element LG is notlimited to the above-described example. For example, the optical layer60 having the openings OP may be formed on the first surface 50A byprinting. Alternatively, after the openings OP are formed in the opticallayer 60 by die cutting, etc., the optical layer 60 may be arranged onthe first surface 50A.

FIG. 12 is a plan view showing another example of the optical layer 60.The example shown in FIG. 12 differs from the example shown in FIG. 10in that the number of the openings OP per unit area varies in the seconddirection Y. That is, in the example shown in FIG. 12, the area of eachopening OPa and the area of each opening OPb are equal to each other,but the number of the openings OPb is greater than the number of theopenings OPa. Therefore, the total area of the openings OPb is largerthan the total area of the openings OPa. The same effect as thatproduced from the example shown in FIG. 10 can also be produced from thepresent example.

FIG. 13 is a plan view showing another example of the optical layer 60.The example shown in FIG. 13 differs from the example shown in FIG. 10in that both the area of the opening OP and the number of the openingsOP per unit area vary in the second direction Y. In the example shown inFIG. 13, the area of each opening OPb is larger than the area of eachopening OPa. Further, the number of the openings OPb is greater than thenumber of the openings OPa. Therefore, the total area of the openingsOPb is larger than the total area of the openings OPa. Even if the areaof each opening OPb is smaller than the area of each opening OPa, thetotal area of the openings OPb may become larger than the total area ofthe openings OPa by increasing the number of the openings OPbsubstantially. Further, even if the number of the openings OPb is lessthan the number of the openings OPa, the total area of the openings OPbmay become larger than the total area of the openings OPa by making thearea of the opening OPb substantially larger than the area of theopening OPa. The same effect as that produced from the example shown inFIG. 10 can also be produced from the present example.

FIG. 14 is a plan view showing another example of the optical layer 60.The example shown in FIG. 14 differs from the example shown in FIG. 10in that the openings OP having different areas overlap the single pixelelectrode 13. In the example shown in FIG. 14, among the openings OPoverlapping the pixel electrode 13 a, the area of an opening OPa2located on the side far from the light emitting element LS is largerthan the area of an opening OPa1 located on the light emitting elementLS side. Similarly, among the openings OP overlapping the pixelelectrode 13 b, the area of an opening OPb2 located on the side far fromthe light emitting element LS is larger than the area of an opening OPb1located on the light emitting element LS side. The same effect as thatproduced from the example shown in FIG. 10 can also be produced from thepresent example.

FIG. 15 is a sectional view showing another example of the displaydevice DSP. The example shown in FIG. 15 differs from the example shownin FIG. 2 in that the light emitting element LS is located directlybelow the extension portion Ex. In the example illustrated, the edge E32of the light guide layer 50 is located between the edge 512 of the firstsubstrate SUB1 and the edge E22 of the second substrate SUB2 in thesecond direction Y. The light emitting element LS entirely overlaps thefirst substrate SUB1. The same effect as that produced from the exampleshown in FIG. 2 can also be produced from the present example. Further,since the light emitting element LS overlaps the extension portion Ex,the width of the non-display area NDA which does not contribute todisplay can be reduced, and consequently, the frame can be narrowed.

FIG. 16 is a sectional view showing another example of the displaydevice DSP. The example shown in FIG. 16 differs from the example shownin FIG. 15 in that the light guide element LG is located on the secondsubstrate SUB2 side. That is, the first surface 50A is opposed to thesecond substrate SUB2. The adhesive layer 70 contacts the light guidelayer 50, the optical layer 60 and the second substrate SUB2. The lightemitting element LS is located directly above the extension portion Exand entirely overlaps the first substrate SUB1. In the exampleillustrated, the edge E32 overlaps the edge E22. The same effect as thatproduced from the example shown in FIG. 15 can also be produced from thepresent example.

FIG. 17 is a sectional view showing another example of the displaydevice DSP. The example shown in FIG. 17 differs from the example shownin FIG. 2 in that the display device DSP further includes optical layers61 and 62. The refractive index of the optical layer 61 and therefractive index of the optical layer 62 are lower than the refractiveindex of the light guide layer 50. For example, the optical layers 61and 62 are formed of the same material as that of the optical layer 60.In other words, the refractive index of the optical layer 61 and therefractive index of the optical layer 62 are equal to the refractiveindex of the optical layer 60.

The optical layer 61 contacts the entire second surface 50B. That is,the optical layer 61 is provided in an area between the edge E31 and theedge E32 in the second direction Y. The optical layer 62 contacts theentire upper surface 20T. That is, the optical layer 62 is provided inan area between the edge E21 and the edge E22 in the second direction Y.The optical layers 61 and 62 do not have openings. The light travelingthrough the display panel PVL and the light guide element LG is alsoreflected at the border of the light guide layer 50 and the opticallayer 61 (that is, by the second surface 50B) and the border of thesecond substrate SUB2 and the optical layer 62 (that is, by the uppersurface 20T) in addition to the border of the light guide layer 50 andthe optical layer 60 and the border of the adhesive layer 70 and theoptical layer 60.

The same effect as that produced from the example shown in FIG. 2 canalso be produced from the present example. Further, according to thepresent example, even if foreign materials such as drops of water are ona surface 61A of the optical layer 61 and a surface 62A of the opticallayer 62, the light traveling through the display panel PNL and thelight guide element LG are reflected off the second surface 50B and theupper surface 20T with reflection conditions thereof unchanged. That is,it is possible to prevent scattering of light caused by foreign matterson the surfaces of the display device DSP and prevent decrease of theefficiency of usage of light.

FIG. 18 is a diagram showing the main structural elements of the displaydevice DSP shown in FIG. 1. The display device DSP includes a controllerCNT shown by a dotted line in the drawing. The controller CNT includes atiming controller TC, the gate drivers GD1 and GD2, the source driverSD, a Vcom circuit VC, a light source driver LSD, etc. The timingcontroller TC generates various signals based on image data, asynchronization signal, etc., which are input from the outside. Forexample, the timing controller TC outputs a video signal generated frompredetermined signal processing of the image data to the source driverSD. Further, the timing controller TC outputs control signals generatedbased on the synchronization signal to the gate drivers GD1 and GD2, thesource driver SD, the Vcom circuit VC and the light source driver LSD,respectively.

A scanning signal is supplied to each scanning line G from the gatedriver GD1 or GD2. A video signal is supplied to each signal line S fromthe source driver SD. A common voltage is applied to the commonelectrode 21 from the Vcom circuit VC. The video signal supplied to thesignal line S is supplied to the pixel electrode 13 connected to theswitching element SW during a period in which the switching element SWis conductive based on the scanning signal supplied to the scanning lineG. A high-level voltage is applied to the scanning line G as thescanning signal during a period in which the switching element SW isconductive, and a low-level voltage is applied to the scanning line G asthe scanning signal during a period in which the switching element SW isnonconductive. For example, the high-level voltage is +20 V and thelow-level voltage is −20 V. If the common electrode 21 is set to avoltage of 0 V as the common voltage, a potential difference of 20 V isproduced not only between the common electrode 21 and the scanning lineG which is subjected to the high-level voltage but also between thecommon electrode 21 and the scanning line G which is subjected to thelow-level voltage. In the present embodiment, leakage of light caused byundesired scattering of light of the liquid crystal layer 30 can beprevented between the scanning line G and the common electrode 21 byapplying the above-described first to third structural examples.

The light source unit LU includes, for example, a light emitting element(first light emitting element) LSR which emits light having the firstcolor, a light emitting element (second light emitting element) LSGwhich emits light having the second color, and a light emitting element(third light emitting element) LSB which emits light having the thirdcolor. For example, the first color is red, the second color is greenand the third color is blue. The dominant emission wavelength of thelight emitting element LSR is 622 nm, for example. The dominant emissionwavelength of the light emitting element LSR is 531 nm, for example. Thedominant emission wavelength of the light emitting element LSB is 466nm, for example. The light emitting elements LSR, LSG and LSB arearranged in the extension direction of the scanning lines G (the firstdirection X). Further, the light emitting elements LSR, LSG and SLB areopposed to the edge E22.

The light source driver SD controls the lighting periods of the lightemitting elements LSR, LSG and LSB according to the control signals fromthe timing controller TC, etc. In a driving mode in which one frame hasa plurality of sub-frames (fields), at least one of the three lightemitting elements LSR, LSG and LSB is lighted, and the color ofillumination light is switched sub-frame by sub-frame.

As described above, according to the present embodiment, a displaydevice which can prevent degradation of display quality can be provided.

In the present embodiment, the light guide layer 50 corresponds to thelight guide layer. The first surface 50A corresponds to the firstsurface, the second surface 50B corresponds to the second surface, andthe edge E32 corresponds to the edge or the first edge. The edge E12 ofthe first substrate SUB1 corresponds to the second edge. The edge E22 ofthe second substrate SUB2 corresponds to the third edge. The opticallayer 60 corresponds to the first optical layer. The pixel electrode 13a corresponds to the first pixel electrode, and the pixel electrode 13 bcorresponds to the second pixel electrode. The opening OPa correspondsto the first opening, and the opening OPb corresponds to the secondopening. The opening OPa1 corresponds to the third opening, the openingOPa2 corresponds to the fourth opening, the opening OPb1 corresponds tothe fifth opening, and the opening OPb2 corresponds to the sixthopening. The upper surface 20T corresponds to the third surface. Theoptical layer 61 corresponds to the second optical layer, and theoptical layer 62 corresponds to the third optical layer.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A display device comprising: a display panelincluding a first substrate, a second substrate which is opposed to thefirst substrate, a sealant which is located between the first substrateand the second substrate, and a polymer dispersed liquid crystal layerwhich is located within an area surrounded by the sealant and contains apolymer and a liquid crystal molecule; a light emitting element; a lightguide layer having a first surface which is opposed to the displaypanel, and a first edge which is opposed to the light emitting element;a first optical layer which contacts the first surface between thesecond substrate and the light guide layer and extends from the firstedge to a position overlapping at least the sealant; and an adhesivelayer located between the display panel and the light guide layer,wherein a refractive index of the first optical layer is lower than arefractive index of the light guide layer, the first substrate has asecond edge located on a light emitting element side, the secondsubstrate has a third edge located on the light emitting element side,the first substrate has an extension portion between the second edge andthe third edge, the light emitting element is located between the secondedge and the third edge and is provided directly above the extensionportion, the second substrate is located between the first substrate andthe light guide layer, the adhesive layer contacts the second substrateand the light guide layer, the adhesive layer is located between thesecond substrate and the first optical layer, a refractive index of theadhesive layer is higher than the refractive index of the first opticallayer, and is the same as a refractive index of the first substrate andthe refractive index of the light guide layer, and the first opticallayer includes a plurality of openings which are filled with theadhesive layer.
 2. The display device of claim 1, wherein the displaypanel includes a first pixel electrode, and a second pixel electrodewhich is far from the light emitting element than the first pixelelectrode, the first optical layer includes a first opening whichoverlaps the first pixel electrode, and a second opening which overlapsthe second pixel electrode, and an area of the second opening is largerthan an area of the first opening.
 3. The display device of claim 1,wherein the display panel includes a first pixel electrode, and a secondpixel electrode which is far from the light emitting element than thefirst pixel electrode, the first optical layer has a first openingswhich overlap the first pixel electrode, and second openings whichoverlap the second pixel electrode, and a number of the second openingsis greater than a number of the first openings.
 4. The display device ofclaim 1, wherein the display panel further includes a first pixelelectrode, the first optical layer includes a third opening and a fourthopening which overlap the first pixel electrode, the fourth opening isfar from the light emitting element than the third opening, and an areaof the fourth opening is larger than an area of the third opening. 5.The display device of claim 4, wherein the display panel furtherincludes a second pixel electrode which is far from the light emittingelement than the first pixel electrode, the first optical layer includesa fifth opening and a sixth opening which overlap the second pixelelectrode, the sixth opening is far from the light emitting element thanthe fifth opening, an area of the fifth opening is larger than the areaof the fourth opening, and an area of the sixth opening is larger thanthe area of the fifth opening.
 6. The display device of claim 1, whereinthe display panel further includes an extension portion, and the firstoptical layer is provided in an area which overlaps at least theextension portion.
 7. The display device of claim 6, wherein the lightemitting element overlaps the extension portion.
 8. The display deviceof claim 1, further comprising a second optical layer and a thirdoptical layer which have a refractive index lower than the refractiveindex of the light guide layer, wherein the light guide layer has asecond surface which is opposite to the first surface, the display panelhas a third surface which is opposite to a surface opposed to the lightguide layer, the second optical layer contacts the entire secondsurface, and the third optical layer contacts the entire third opticallayer surface.
 9. A display device comprising: a display panel includinga first substrate, a second substrate which is opposed to the firstsubstrate, a sealant which is located between the first substrate andthe second substrate, and a polymer dispersed liquid crystal layer whichis located within an area surrounded by the sealant and contains apolymer and a liquid crystal molecule; a light emitting element; a lightguide layer having a first surface which is opposed to the displaypanel, and a first edge which is opposed to the light emitting element;a first optical layer which contacts the first surface between the firstsubstrate and the light guide layer and extends from the first edge to aposition overlapping at least the sealant; and an adhesive layer locatedbetween the display panel and the light guide layer, wherein arefractive index of the first optical layer is lower than a refractiveindex of the light guide layer, the first substrate has a second edgelocated on a light emitting element side, the second substrate has athird edge located on the light emitting element side, the firstsubstrate has an extension portion between the second edge and the thirdedge, the light emitting element is located between the second edge andthe third edge and is provided directly under the extension portion, thefirst substrate is located between the second substrate and the lightguide layer, the adhesive layer contacts the first substrate and thelight guide layer, the adhesive layer is located between the firstsubstrate and the first optical layer, a refractive index of theadhesive layer is higher than the refractive index of the first opticallayer, and is the same as a refractive index of the first substrate andthe refractive index of the light guide layer, and the first opticallayer includes a plurality of openings which are filled with theadhesive layer.
 10. The display device of claim 9, wherein the firstsubstrate has a second edge located on a light emitting element side,the first edge and the second edge extend in a first direction, aposition of the first edge and a position of the second edge are alignedwith each other in a second direction which intersects the firstdirection.
 11. The display device of claim 9, wherein the secondsubstrate has a third edge located on a light emitting element side, thefirst edge and the third edge extend in the first direction, and aposition of the first edge and a position of the third edge are alignedwith each other in a second direction which intersects the firstdirection.
 12. The display device of claim 9, wherein the firstsubstrate has a second edge located on a light emitting element side,the second substrate has a third edge located on a light emittingelement side, the first edge, the second edge and the third edge extendin the first direction, the first edge is located between the secondedge and the third edge in a second direction which intersects the firstdirection.
 13. The display device of claim 9, further comprising: asecond optical layer and a third optical layer which have a refractiveindex lower than the refractive index of the light guide layer, whereinthe light guide layer has a second surface which is opposite to thefirst surface, the display panel has a third surface which is oppositeto a surface opposed to the light guide layer, the second optical layercontacts the entire second surface, and the third optical layer contactsthe entire third surface.